The prior art includes magnetic pumps comprising a pump body to house the motor connected to a drive shaft, and a hermetically sealed chamber or volute with an inlet and outlet for the liquid to circulate, inside of which at least one impeller coupled with a pump shaft rotates.
The drive of said pump shaft, and therefore of the impeller, is achieved through an internal magnet coupled to said drive shaft, said internal impeller being driven by a magnet of the drive shaft, or by an external magnet.
In magnetic pumps of the known type said volute or hydraulic component is partially constituted by a rear body firmly fixed to the pump body and partially by another portion constituted by a lid connectable to the pump body.
This rear body of magnetic pumps of a known type comprise a glass-shaped casing placed between said external magnet and said internal magnet.
The use of probes to monitor the pump's operating parameters is a known technique.
In particular, the use of probes to monitor the temperature of said rear body is known, said probes being bound to said rear body in the area affected by the magnetic field.
The magnetic field generated by the external rotating magnet induces a current in the rear body, if made of metal material, which heats the rear body. Under normal operating conditions, the rear body is cooled when the pump is running.
Nonetheless the temperature must be constantly monitored because, in the case of malfunctions, sudden increases in temperature may occur that require timely maintenance and repair interventions.
These increases in temperature of pump parts may damage the pump or even cause fires or explosions, especially in the case where flammable fluids are pumped.
Patents EP 0 610 562 and EP 1 091 128 relate to magnetic pumps with a temperature sensor installed on the glass-shaped casing, and where said sensor comprises a thermocouple that has a conductor formed by the glass-shaped casing itself and the other conductor is attached to the surface of the glass-shaped casing.
This sensor may for example comprise a flat terminal located on the surface of the glass-shaped casing facing the external magnet.
Glass-shaped casings of the known type essentially have a structural function, being containers under pressure.
Glass-shaped casings made entirely of metal, which involve magnetic losses inside the magnetic field, or made entirely of non-metal material are already known.
However, pumps with non-metal glass-shaped casings cannot be used in environments such as refineries and petrochemical plants where the fluids being pumped cannot come into contact with non-metal surfaces.
Patents DE 4342649, U.S. Pat. No. 4,854,823 and JP 63-257451 relate to magnetic pumps equipped with composite glass-shaped casings, that is, comprising an external wall made of a different material from the internal wall.